Originally posted by jgnfld To my mind, UWA focal lengths are often best used at close range period.
At a distance, compressing so much material onto an APSC sensor just loses clarity. A stitched panorama, if possible, often looks better. I don't think I'm alone in this opinion.
Subject-wise, that's almost a given, but I don't think it depends on the APS-C sensor
tout-court, rather on pixel density.
I was talking optically, since my copy's plane of focus is not perfectly planar (or approximately, or at least uniformely curved), rather is a little bit deformed so the far right side tends to focus a bit closer than the rest of the image.
This is only evident at long distances, thus my remark on my particular copy of this lens.